1. Field of the Invention
This invention relates to an image forming apparatus for use in a copying machine, a printer, a plotter, a facsimile machine, or similar machine.
2. Description of Related Art
One image forming apparatus that has been conventionally known is an image forming apparatus disclosed in U.S. Pat. No.3,689,935, which uses an electrode having plural opening portions (hereinafter referred to as "apertures ") formed therein. In this image forming apparatus, a voltage is applied to the electrode on the basis of image data to control the passage of toner particles through the apertures. An image (toner image) is formed on a supporter with the passed toner particles.
This image forming apparatus includes an aperture electrode member comprising an insulating flat plate, a reference electrode having a continuous body formed on one surface of the flat plate, plural control electrodes, which are insulated from one another, formed on the other surface of the flat plate, and at least one array (row) of apertures, each of which is formed in correspondence with each control electrode so as to be penetrated through the flat plate, the reference electrode and the control electrode. The image forming apparatus further includes means for selectively applying potential across the reference electrode and each of the control electrodes. Also provided are means for supplying charged toner particles so that the flow of the toner particles passed through the apertures is modulated on the basis of the applied potential and means for positioning the supporter in a particle-flow passage so that the supporter and the aperture electrode member are relatively movable.
However, in the above conventional image forming apparatus, the apertures or the opening portions are arranged in a row so that print density cannot be sufficiently heightened. In addition, when plural arrays (rows) of apertures or opening portions are used to heighten the print density, the density of an image on each line (in correspondence with each row of apertures) is different from that on another line. Thus, image quality is lowered.